Variable delay line



Aug. 7, 1956 J. F. PEOPLES VARIABLE DELAY LINE Filed April 2, 1953 OUTPUT FEGJ.

INVENTOR JOHN F. PEOPLES RM Mi h ATTORNEYS United States Patent @fifice 2,758,284 i atented Aug. 7, 1956 VARIABLE DELAY LINE John F. Peoples, Indianapolis, Ind., assignor to the United 'States of America as represented by the Secretary of the Navy Application April 2, 1953, Serial No. 346,548

5 Claims. (Cl. 333P-31) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to an electronic circuit component and more specifically to a variable delay line for altering the transmission time of an electrical signal.

More particularly the delay line component incorporates transformer loading principles to vary the inductance per unit length thereof and hence the delay time characteristics of the instant circuit.

Prior time delay devices for circuitry of the character for which the instant invention is intended have accomplished the variation of delay time by moving an adjustable contact along the delay line proper, thereby to vary the physical length of the line. Certain devices of this nature impose operational disadvantages such as wearing of the conductor caused by the moving contact.

The instant delay line incorporates a cylindrical nonconducting ferromagnetic core of a material of the group known in the trade as ferrites with a spirally wound inductance winding thereon, and a second winding inductively coupled thereto which functions as a variableloaded transformer secondary by which the control is varied by changing an adjustable resistance in the circuit thereof. This winding functions to control the impedance of the delay line winding on the saturable core and hence the inductance per unit length and the delay time. Variations of the control resistance across the control inductance winding changes the degree of transformer loading reflected back to the delay line inductance to alter the incremental inductance thereof.

It is a feature of this invention to provide a high impedance continuously variable delay line for delaying the transmission time of an electrical signal in a manner overcoming the low impedance disadvantages of delay lines heretofore or now in general use which inherently produce low impedance characteristics.

One object of the instant invention resides in the provision of improved means utilizing core materials possessing desirable saturable reactor characteristics to vary the delay in the transmission time of an electrical signal.

Another object resides in the utilization of distributed transformer loading action to vary the inductance per unit length of a delay line.

Another object lies in providing continuously variable time delay in the order of microseconds in an artificial delay line device of reduced physical dimensions over delay lines heretofore or now in general use.

It is also an object to utilize a variable resistance across a control winding to vary the delay time of an electrical signal in an artificial delay line.

Another object resides in the provision of an improved artificial delay line of an inductance-capacitance character displaying increased time delay per unit volume of delay line.

In correlation with the immediately preceding object it is a further object to provide an L-C type delay line 2 displaying characteristics falling betwen a lumped constant, and distributed constant network.

Still another object is to reduce the attenuation of a high impedance type delay line with frequency.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. l is a diagrammatical illustration of the delay line component of the instant invention;

Fig. 2 is an exaggerated sectional view of a delay line taken along the plane of 2-2 of Fig. 1; and

Fig. 3 is a schematic diagram of the equivalent circuit of the delay line.

Referring now to Figs. 1 and 2 of the drawings, a delay line component is indicated generally at l. The assembly generally comprises a core 2, a delay line inductance winding 3 and a control winding generally indicated at 4 which is adapted for resistance adjustment by the variable resistor 5.

The core 2, Fig. 2, shown in cylindrical form, may be of toroidal configuration, and is of a suitable non-conducting ferromagnetic material such as one of the ferrite-s as they are known in the trade, or an equivalent. A layer of insulating tape 6 is wrapped about this core to provide a base for the application of electrical conducting silver paint, after which the tape and paint are slotted longitudinally about the peripheral surface of the cylinder '7 to reduce eddy current effects and provide a plurality of metallic bars or strip plates 8 which are electrically connected to provide the capacitance of the network.

It is to be understood that the inductance winding 3 which is insulated from the plates 8 by a second layer of insulating tape 9 (Fig. 2), and wound thereover, may be built up in a manner wherein the winding is divided and wound in a distributed manner below and over the capacitance strips 8 in a sandwich relationship. The individual control winding turns 11 of the winding 4- having the variable resistance 5 in the circuit thereof, is distributed over the turns 12 of the inductance winding 3.

A more efiicient utilization of the core may be accomplished if the configuration thereof is such that the assembly takes the form of a toroid. This form is not shown since the schematic representation of Fig. 1 is substantially the equivalent if the two ends are considered as being brought together to form a circle.

The silver strips or plates 8 which comprise the capacitance C of Fig. 3 are each electrically connected to a conductor band 13 by drops of silver paint at 16. The leads 14 and 15 from this conductor 13 provide the common input and output terminals of the delay line 1.

As shown in Fig. 3, the inductance winding 3 comprises a plurality of turns 12, each of which provides an incremental time delay in a circuit relationship Fig. 3, which may arbitrarily be considered as a lumped constant T network as hereinafter set forth with respect to the description of the schematic.

In the showing of Fig. 3, the lumped constant electrical equivalents of one section of the filter corresponding to one turn 12 of the winding about the core assembly is illustrated schematically. The electrical resistance of each half of the winding is indicated by R/2 while the inductance of each half turn is indicated L/2, with the shunt capacitance of the T section indicated at C. The leakage conductance in shunt with the capacitance is indicated at G.

The control winding 1.1/2 as represented in Fig. 3 is shown for a one turn relationship with the variable control resistance 5 thereacross although in practice this resistance is across all the turns of the control winding rather than each turn individually as with the schematic illustration.

In practice the input and output of the delay line are terminated with the characteristic impedance thereof to minimize reflections.

Time delay variations in microseconds of the order of 1 to microseconds is accomplished by changing the short circuiting resistance 5 in the winding 4 and thereby altering the magnetic state of the saturable reactor or transformer loading in the event the core is not operated in a manner to drive it into saturation.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention'rnay be practiced otherwise than as specifically described.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A continuously variable artificial delay line device comprising: a non-conducting ferromagnetic core; a'delay line inductance having first input and output leads wound on said core; means providing a capacitance with respect to the delay line inductance said means including a conductive capacitor plate having second input and output leads, said first and second input leads constituting a signal input circuit and said first and second output leads constituting a signal output circuit; a second inductance on said core and disposed in inductively coupled relation to said first inductance; and a variable resistance connected across said second inductance to provide variable control of the delay time.

2. A variable artificial delay line device of the character described for delaying an electrical signal passing therethrough comprising: a non-conducting ferromagnetic core, a plurality of conductive segments longitudinally coextensive with said core and equidistantly spaced'about the peripheral surface thereof, a single conductor electrically connected to one end of said plurality of segments and forming a common conductor of said delay line, an insulated inductance winding Wound about said plurality of segments in coaxial alignment therewith, a secondary winding about said core coupled inductively to the said inductance winding and in coaxial alignment with the said core and with said inductance winding, a

resistor connected across said secondary winding, one end i of said inductance winding and one end of said conductor being the input terminals of said device to which said electrical signal is applied, the other end of said winding and the other end of said conductor being the output terminals of said delay device, and means for varying the resistance of the said resistor to vary the time delay through said artificial delay line.

3. A transformer-type artificial delay line apparatus for pre-setting and changing a delay-in-transit time for electrical signals transmitted therethrough comprising in combination: a nonconductive ferromagnetic core having peripheral surfaces; a first capacitor element disposed in juxtaposition and substantially coextensive with the said peripheral surfaces said first capacitor element having first input and output leads; a dielectric medium disposed on the surface of the said first capacitor element; a second capacitor element comprising a primary inductive winding having second input and output leads to conduct the said electrical signals to be delayed wound on the said dielectric medium such that the said first capacitor element, dielectric medium, and second capacitor element comprise a capacitor having a fixed capacitance, the said first and second input leads constituting a signal input circuit and the said first and second output leads constituting a signal output circuit'for the said capacitor; 21 secondary inductive Winding disposed on the said core in inductive coupling relation with the said primary inductive winding, said secondary winding having connecting leads; and means connected across the said connecting leads for controlling the degree of inductive loading on the said primary inductive winding and, as a result, establishing the delay time for signals to be transmitted through the said primary winding.

4. An electrical-signal delay line comprising in combination: a nonconductive winding form; first means operative as a capacitor plate disposed over atleast a portion of the surface of said Winding form, said first means having first input and output leads; second means disposed over at least a portion of the surface of the said first means including conductive means for passing an electrical signal to be delayed and dielectric means disposed between the said first means and the said conductive means, the said conductive'means also eifectivc as another capacitor plate suchthat a fixed predetermined capacitance is established between 'thesaid first means and the conductive means; second input and output leads connected to the said conductive means, the said first and second input leads constituting a signal input circuit and the said first and second output leads constituting a signal output circuit; third means coupled inductively to the said conductive means, the said third means including connecting leads; means connected to the said connecting leads'constituting a passive load for the said third means; and fourth means for changing the magnitude of the said passive load so that, as a result, the delay in the transit time'of the said electrical signal through the said conductive means may be preset and changed continuously.

5. A transformer-type, variable delay time, artificial delay line comprising in combination: a cylindrical core; a first capacitor component having a plurality of mutually insulated plate elements disposed on the cylindrical surface of said core; a dielectric medium disposed over the said capacitor component; a delay-line primary inductive winding around said dielectric medium to provide a second capacitor component; first input and output leads for-the-said delay-line primary inductive winding; a con ductor having second output and input leads connected electrically to thesaid plate elements to'insure the existence of a commorr potential on each plate, and such that the said'first and second input leads constitute a signal input circuit and thesaid-first and second output leads constitute a signal output circuit; a secondarycontrol winding disposed on the said core ininductive coupling relation withthe said primaryinductive winding, said secondary control winding having conductive output leads; first means connected to thesaid conductive output leads to provide a passive electrical load; and second means to varythe'said passive electrical load'of the said firstmeans and, as a result, effectuate correspondingchanges.in'the delay-time characteristic of'the said delay .line.

References Cited in-the file of this patent UNITED STATES PATENTS 1,533,178 Gilbert Apr. 14, 1925 2,258,261 Roosenstein Oct. 7, 1941 2,461,061 Kallmann 'Feb. 8, 1-949 2,522,731 Wheeler Sept! 19, 1950 2,540,560 Wheeler Feb. 6, 1951 2,619,537 Kihn Nov. 25, 1952 2,650,350 Heath Aug. 25, 1953 

